1. Field of the Invention
This invention relates to a two-pack aqueous coating composition comprising a first pack component of water-dispersible acrylic copolymer and a second pack component of polyisocyanate.
2. Description of Related Art
The restriction on any organic solvent release into atmospheric air has been constantly tightened in the recent years, for environmental and sanitary considerations. Paints are no exception and, hence, shifting from organic solvent-dissolved paints to aqueous paints is under progress. In particular, provision of aqueous crosslinking paints is drawing attention because of their favorable weatherability, solvent-resistance and appearance. As compositions meeting the object, aqueous urethane coating compositions have been proposed, the typical examples being two-component polyurethane aqueous paint compositions (cf. U.S. Pat. Nos. 5,075,370 and 4,711,918).
Such two-component polyurethane aqueous paint compositions almost invariably use an aqueous solution, aqueous dispersion or aqueous emulsion of hydroxyl-containing olefinic unsaturated compounds, and are subject to a defect that their initial hardening is slow in the drying during the first through third days after painting, at temperatures not higher than 40.degree. C., in particular, at normal temperature. Also in respect of physical properties, it is difficult to obtain from them a paint film excelling in both tensile strength and elongation. Furthermore, when an emulsifier is used in the process of preparing such a composition, the emulsifier remains in the paint film to deteriorate its water resistance.